Ajmal C
Member
Decided to go with a bare bottom with live rock for my frag tank. Wanted to keep an aragonite sand bed for 3 reasons. 1) To act as a stabilizing buffer 2) to act as substrate for beneficial microbes to grow on 3)From an 'aesthetically pleasing' perspective . Also having to travel so figured it would be easier.
Realized reason 1 was not true so reasons 2 and 3 can be sacrificed, hoping the live rock and filter media will suffice in keeping the nitrogen waste chemistry in check.
I wanted to discuss whether aragonite sand really has any buffering capacity to maintain pH.
I stumbled upon a ReefCentral thread: http://s.reefcentral.com/forums/showthread.php?t=1008046
Where a chemist and member, Randy Holmes-Farley, and a few others state aragonite sand beds don't offer buffering capacity and in fact diminish it.
Randy Holmes-Farley even has an article in Advanced Aquarist discussing alakalinity and acid /base chemistry in the reef : http://www.advancedaquarist.com/2002/7/chemistry
Not sure if this has been discussed on CR but would love for anyone to chime in with their insights.
From what I understand is that at normal Reef pH (between 8.1 and 8.4) aragonite serves to precipitate Carbonate out of the water, as can be seen by growing coralline algae and coral skeletons (used as calcium carbonate). Initially there may be minute buffering but eventually the aragonite will start precipitating the carbonate out from the water lowering the pH to 7-7.5.
Only at lower pH of say 6.5 and lower will the carbonate in the aragonite start dissolving and contributing to alakalinity and hence increasing and stabilizing the pH. This pH is far below what reefers normally keep their tanks at.
The only place in a reef tank that such pH's may exist is within the anaerobic environment of a Deep Sand Bed, and it's overall efficacy is apparently debatable. I was very general with the chemical terms, chemistry was never my forte, if you feel I am incorrectly stating the chemistry feel free to correct me.
So I decided to opt out of a regular (non deep) sand bed since it really wont stabilize the pH and may even contribute to a pH drop and will make cleaning in my frag tank much harder. Will miss the natural beauty of sand in a reef though.
Reefs with sand beds are only able to maintain a stable pH by ensuring that alakalinity, Calcium and Magnesium are within desirable parameters, but, these are maintained by adding them back into the aquarium and not by just a one time addition of aragonite sand during initial set up of a tank. This is especially true of reef aquariums that suck Calcium carbonate out of the water faster like a tank dominated with Stony corals and coralline algae.
It has also been mentioned that the main culprit for pH drops is Carbon dioxide. CO2 can rise when respiration (during the night) is occurring within corals as opposed to photosynthesis. Excess waste can also produce excess acid which can bring pH down as well. Lack of proper ventilation or gas exchange with the air may also contribute to a relative CO2 rise.
Realized reason 1 was not true so reasons 2 and 3 can be sacrificed, hoping the live rock and filter media will suffice in keeping the nitrogen waste chemistry in check.
I wanted to discuss whether aragonite sand really has any buffering capacity to maintain pH.
I stumbled upon a ReefCentral thread: http://s.reefcentral.com/forums/showthread.php?t=1008046
Where a chemist and member, Randy Holmes-Farley, and a few others state aragonite sand beds don't offer buffering capacity and in fact diminish it.
Randy Holmes-Farley even has an article in Advanced Aquarist discussing alakalinity and acid /base chemistry in the reef : http://www.advancedaquarist.com/2002/7/chemistry
Not sure if this has been discussed on CR but would love for anyone to chime in with their insights.
From what I understand is that at normal Reef pH (between 8.1 and 8.4) aragonite serves to precipitate Carbonate out of the water, as can be seen by growing coralline algae and coral skeletons (used as calcium carbonate). Initially there may be minute buffering but eventually the aragonite will start precipitating the carbonate out from the water lowering the pH to 7-7.5.
Only at lower pH of say 6.5 and lower will the carbonate in the aragonite start dissolving and contributing to alakalinity and hence increasing and stabilizing the pH. This pH is far below what reefers normally keep their tanks at.
The only place in a reef tank that such pH's may exist is within the anaerobic environment of a Deep Sand Bed, and it's overall efficacy is apparently debatable. I was very general with the chemical terms, chemistry was never my forte, if you feel I am incorrectly stating the chemistry feel free to correct me.
So I decided to opt out of a regular (non deep) sand bed since it really wont stabilize the pH and may even contribute to a pH drop and will make cleaning in my frag tank much harder. Will miss the natural beauty of sand in a reef though.
Reefs with sand beds are only able to maintain a stable pH by ensuring that alakalinity, Calcium and Magnesium are within desirable parameters, but, these are maintained by adding them back into the aquarium and not by just a one time addition of aragonite sand during initial set up of a tank. This is especially true of reef aquariums that suck Calcium carbonate out of the water faster like a tank dominated with Stony corals and coralline algae.
It has also been mentioned that the main culprit for pH drops is Carbon dioxide. CO2 can rise when respiration (during the night) is occurring within corals as opposed to photosynthesis. Excess waste can also produce excess acid which can bring pH down as well. Lack of proper ventilation or gas exchange with the air may also contribute to a relative CO2 rise.
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